wa·ter·tight 
/ˌwɑ:tɚˈtaɪt/ adjective
/ˌwɑ:tɚˈtaɪt/ adjective 1 : put or fit together so tightly that water cannot enter or pass through
▪ The doors/compartments are all watertight. ▪ a watertight seal 2 : too strong or effective to fail or to be defeated
▪ The evidence against the defendant was watertight. ▪ a watertight alibi/case
▪ The doors/compartments are all watertight. ▪ a watertight seal
▪ The evidence against the defendant was watertight. ▪ a watertight alibi/case
